Anything under 230 duration at .050 is relatively mild. The lope you hear in the idle is a product of the valve overlap 35 deg overlap or less is mellow...
The lift may make the cam get a bit more HP but it doesn't say anything about how mild or radical a cam is. The longer the duration the more radical a cam is considered. Duration has to be considered in conjunction with the overlap (the number of degrees that both valves are held open at the end of the exhaust and beginning of the intake stroke) to figure out how the cam will behave in the engine. Short overlap keeps the idle smooth but restricts the power produced at higher rpm (with a tuned intake and exhaust). Long overlap will let the exhaust pull air into the cylinders through the opening intake but at lower speeds the long overlap can leave some exhaust gasses in the cylinder or pull too much of the intake charge into the exhaust making the engine run lean or inconsistent fuel mixtures. (that is what causes the lope) For me a mild cam is one that has a smooth idle - no perceptible lope at all. This type includes most of the RV cams and one or two steps above the RV level. (up to 218 duration at .050" lift. At 220 degrees at .050" lift the engine begins to lope at 650 - 700 RPM which is where I like my engines to idle. Another way to look at it is the rpm where the cam allows maximum torque and hp to be generated. Anything (in a 302) that gets peak power above 5000 rpm is no longer mild because it requires stronger than stock parts to withstand sustained engine speed at that level. Strong, lightweight pistons and stronger rods and rod bolts are required above 5000 - 5500 rpm to keep the engine from failure due to inertia effects on the reciprocating parts. I consider cams in this duration "moderate" cams. Much above 6500 rpm requires a stronger crank and modifications to the oiling system and a windage tray or scraper to keep the oil from clinging to the crankshaft. I consider those "radical cams". Defining a cam as mild, moderate and radical is a very subjective way to describe a cam. What is radical to me might be mild to someone else. It is always best to describe a cam in duration at .050" lift and the overlap angle. In addition to these values the actual timing events (registered in degrees) tells the whole story of the cam.
That used to be the thought behind this, but the trend now is to use wider LSA cams in all applications, they really don't affect the HP produced in the upper rpms of most engines. The benefit here is a better bottom end, without sacrificng the upper rpms
